1. Field of the Invention
This invention relates to self-inverting water-in-oil polymer emulsions having low pour point temperatures for use in industrial water treatment, waste water treatment, sludge conditioning, ore dressing, papermaking, secondary and tertiary oil recovery.
2. Description of the Prior Art
Water-in-oil self-inverting polymer emulsions are used in commercial applications such as industrial water treatment, waste water treatment, sludge conditioning, ore dressing, papermaking, secondary and tertiary oil recovery.
Three types of polymer emulsions, i.e., nonionic, cationic and anionic emulsions are known. Preparation of these emulsions is described in numerous patents. The internal phase of the emulsion is formed from a water solution of an ethylenic unsaturated monomer or comonomer such as (1) acrylamide, methacrylamide, (2) acrylic acid, methacrylic acid, (3) dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethyl and diethylaminoethyl acrylate, allyl methacrylate and its quaternization products, (4) N-substituted methacrylamide and (5) vinyl sulfonate.
The external phase of the emulsion is formed using low HLB emulsifiers such as mono and diglycerides of fatty acids, sorbitan fatty acid monoesters, polyoxyethylene alcohols and the like dissolved in a solvent such as kerosene, xylene, toluene and chlorinated hydrocarbons.
A water-in-oil emulsion is produced by slowly adding the water phase to the oil phase under rapid agitation. The emulsion is homogenized to obtain the proper particle size and is then polymerized by one of the procedures described in the literature. After polymerization is completed, the final step is the incorporation of an inverting agent, a high HLB surfactant, into the emulsion. The finished emulsion is uniform and disperses instantly by self-inversion in a water system. Water-in-oil emulsions and their uses have been described in the prior art. The following patents are representative of the prior art.
U.S. Pat. No. 3,284,393--Vanderhoff et al, issued Nov. 8, 1966, describes polymerization of vinyl monomer in the oil phase by forming a water-in-oil emulsion of the monomer in a hydrophobic liquid and water with a water-in-oil emulsifier and then polymerizing the emulsion with a free radical catalyst to obtain a polymeric latex where the oil phase is the dispersion medium.
U.S. Pat. No. 4,022,731--Schmitt, issued May 10, 1977, describes a self-inverting water-in-oil emulsion containing an acrylamide polymer in the aqueous phase, hydrocarbon oil, water-in-oil emulsifier and an inverting surfactant mixture containing two sulfosuccinates or one sulfosuccinate and an alkylphenol ethoxylate.
U.S. Pat. No. 4,022,736--Schmitt, issued May 10, 1977, describes a self-inverting water-in-oil emulsion having a copolymer of acrylic acid in the aqueous phase, hydrocarbon oil, water-in-oil emulsifier and an inverting surfactant which is a fatty alcohol ethoxylate.
U.S. Pat. No. 4,077,930--Lim et al, issued Mar. 7, 1978, describes a stable, self-inverting water-in-oil emulsion obtained by emulsifying water soluble vinyl monomer in oil containing at least 20% emulsifier and a free radical catalyst and then polymerizing to obtain a stable polymer emulsion which can be inverted by adding water without any other reagent.
Polymeric flooding in oil recovery operations where polyelectrolytes are added to the flood water has become of greater importance because it provides improved oil recovery in secondary and tertiary operations from petroleum reservoirs.
In the temperate zone, use of self-inverting water-in-oil polymer emulsion systems having pour points above or close to 0.degree. C. do not present problems. However, under arctic conditions, when the same emulsion systems are cooled below 0.degree. C., a thick frozen skin forms initially and the system gradually freezes completely. When these emulsions are transported under heated conditions to remote locations, their performance deteriorates rapidly.
Where a wax bearing oil is cooled below its cloud point, wax precipitates and the oil becomes cloudy. When cooling is continued and the wax bearing oil cooled below its pour point, i.e., the lowest temperature at which the oil will still flow, sufficient wax precipitates to gel the oil and to render the oil no longer flowable or usable for its intended purpose.
Certain additives known as pour point depressants can be added in small amounts to wax bearing oils to depress their pour points. Pour point depressants alter the nature of crystals precipitating from the oil as well as inhibit the tendency of wax crystals to interlock and form a gel. These additives not only arrest crystal growth but also destroy cohesive forces between crystals. Pour point depressants have been used extensively to enhance lubricating oil properties. Further information on the use of pour point depressants in lubricating oils may be found on pages 168 through 178 of V. A. Kalichevsky's Modern Methods of Refining Lubricating Oils--(Reinhold Publishing Corporation, N.Y., N.Y., 1938).
South African Pat. No. 81/4128--Lipowski et al, issued to Diamond Shamrock Corporation describes self-inverting water-in-oil emulsions having low temperature pour points prepared by adding pour point depressants and polyols in amounts effective to lower the pour point and inhibit skin formation on emulsions.